package config

import (
	"fmt"
	"os"

	"git.piksar.eu/piotr/groundstation/internal/osd"
	"git.piksar.eu/piotr/groundstation/internal/protocol"
	"gopkg.in/yaml.v3"
)

// DisplayConfig configures the independent kiosk canvas process.
type DisplayConfig struct {
	Enabled    bool   `yaml:"enabled"`
	Command    string `yaml:"command"`
	User       string `yaml:"user"`
	Display    string `yaml:"display"`
	Xauthority string `yaml:"xauthority"`
}

// OSDConfig configures the supervisor's flight OSD snapshot publication.
type OSDConfig struct {
	// StatePath is the snapshot state file the display process reads.
	StatePath string `yaml:"state_path"`
	// ArmIndex and ArmedThreshold derive the arm state from the final RC
	// channels: armed while that channel stays above the threshold.
	ArmIndex       int   `yaml:"arm_index"`
	ArmedThreshold int16 `yaml:"armed_threshold"`
	// VtxTableGen and VtxTableHash are the operator-selected VTX power
	// table identifiers. Zero means no table is selected yet; a static
	// selection is operator intent and never applied VTX state.
	VtxTableGen  uint32 `yaml:"vtx_table_gen"`
	VtxTableHash uint64 `yaml:"vtx_table_hash"`
}

type Config struct {
	Display DisplayConfig `yaml:"display"`
	Serial  struct {
		Path string `yaml:"path"`
	} `yaml:"serial"`
	Video struct {
		Enabled   bool   `yaml:"enabled"`
		AuxIndex  int    `yaml:"aux_index"`
		Threshold int16  `yaml:"threshold"`
		Command   string `yaml:"command"`
	} `yaml:"video"`
	OSD     OSDConfig `yaml:"osd"`
	Logging struct {
		Enabled bool   `yaml:"enabled"`
		Path    string `yaml:"path"`
	} `yaml:"logging"`
}

func Default() Config {
	var c Config
	c.Display = DefaultDisplay()
	c.Serial.Path = "/dev/ttyS0"
	c.Video.Enabled = true
	c.Video.AuxIndex = 5 // AUX2, zero-based
	c.Video.Threshold = -512
	c.Video.Command = "fpv-video"
	c.OSD = DefaultOSD()
	c.Logging.Enabled = true
	return c
}

// DefaultDisplay starts the kiosk canvas before video on the desktop X
// server owned by the unprivileged display user.
func DefaultDisplay() DisplayConfig {
	return DisplayConfig{
		Enabled:    true,
		Command:    "/usr/local/bin/groundstation-display",
		User:       "orangepi",
		Display:    ":0",
		Xauthority: "/home/orangepi/.Xauthority",
	}
}

// DefaultOSD publishes snapshots to the default tmpfs path and derives the
// arm state from CH5/AUX1, armed above the midpoint.
func DefaultOSD() OSDConfig {
	return OSDConfig{
		StatePath:      osd.DefaultStatePath,
		ArmIndex:       4,
		ArmedThreshold: 0,
	}
}

func Load(path string) (Config, error) {
	config := Default()
	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return config, config.validate()
		}
		return config, err
	}
	if err := yaml.Unmarshal(data, &config); err != nil {
		return config, err
	}
	return config, config.validate()
}

// validate rejects channel indexes outside the final RC channel range: an
// out-of-range index would panic on the first decoded frame.
func (c Config) validate() error {
	for name, index := range map[string]int{
		"video.aux_index": c.Video.AuxIndex,
		"osd.arm_index":   c.OSD.ArmIndex,
	} {
		if index < 0 || index >= protocol.Channels {
			return fmt.Errorf("%s %d outside the RC channel range 0..%d", name, index, protocol.Channels-1)
		}
	}
	return nil
}